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use crate::generator::TaskGenerator;
use crate::task::{Status, Task};
use chrono::prelude::*;
use chrono::Utc;
use log::{debug, error, info, warn};
use std::thread;
use std::time::Duration;
/// Task execution possible statuses.
pub(crate) enum ExecutionStatus {
Success,
HadError(usize),
}
/// Task scheduler and executor.
pub struct TaskScheduler<'a, T>
where
T: TimeZone + Clone,
{
/// The list of tasks to be executed.
tasks: Vec<Task<'a, T>>,
/// The (optional) task generation function.
task_gen: Option<TaskGenerator<'a, T>>,
/// The sleep time in ms.
sleep: usize,
/// The id that shoould be assigned to the next appended task.
next_id: usize,
/// The main timezone used for the scheduler.
timezone: T,
}
/// `TaskScheduler` implementation.
impl<'a, T> TaskScheduler<'a, T>
where
T: TimeZone + Clone,
{
/// Create a new instance of `TaskScheduler` with no tasks to execute.
///
/// # Arguments
///
/// * sleep - The execution frequency (in ms).
/// * timezone - The scheduler's timezone.
///
/// # Examples
///
/// ```
/// # use tasklet::TaskScheduler;
/// // Create a new `TaskScheduler` instance that executes every 1000ms.
/// let _schedule = TaskScheduler::new(1000, chrono::Local);
/// ```
pub fn new(sleep: usize, timezone: T) -> TaskScheduler<'a, T> {
TaskScheduler {
tasks: Vec::new(),
task_gen: None,
sleep,
timezone,
next_id: 0,
}
}
/// Set a `TaskGenerator` inistance for the TaskScheduler.
///
/// # Arguments
///
/// * task_gen - a `TaskGenerator` instance.
///
/// # Examples
///
/// ```
/// # use tasklet::{TaskScheduler, TaskGenerator};
/// // Create a new `TashSceduler` instance and attach an `TaskGenerator` to it.
/// let mut scheduler = TaskScheduler::new(1000, chrono::Local);
/// let mut generator = TaskGenerator::new("1 * * * * * *", chrono::Local, || None);
/// scheduler.set_task_gen(generator);
/// ```
pub fn set_task_gen(&mut self, task_gen: TaskGenerator<'a, T>) -> &mut TaskScheduler<'a, T> {
self.task_gen = Some(task_gen);
self
}
/// Add a new task in the execution queue.
///
/// # Arguments
///
/// * task - a `Task` instance.
///
/// # Examples
///
/// ```
/// # use tasklet::{TaskScheduler, Task};
/// // Create a new `TaskScheduler` and attach a task to it.
/// let mut scheduler = TaskScheduler::new(1000, chrono::Local);
/// // Add a task that executes every second forever.
/// scheduler.add_task(Task::new("* * * * * * *", None, None, chrono::Local));
/// ```
pub fn add_task(&mut self, task: Task<'a, T>) -> &mut TaskScheduler<'a, T> {
self.tasks.push(task);
self
}
/// Execute all the statuses in the queue.
/// After the execution the tasks are rescheduled and if needed,
/// removed from the list.
pub(crate) fn execute_tasks(&mut self) -> ExecutionStatus {
// Ids of the tasks to be removed at the end of iterations.
let mut finished_ids: Vec<usize> = Vec::new();
let total = self.tasks.len();
let mut err_count: usize = 0;
for (index, task) in self.tasks.iter_mut().enumerate() {
if task.next_exec.as_ref().unwrap() <= &Utc::now().with_timezone(&self.timezone.clone())
{
debug!("Executing task {} ({}/{})", task.task_id, index + 1, total);
task.run_task();
if task.status == Status::Failed {
err_count += 1;
}
task.reschedule();
if task.status == Status::Finished {
finished_ids.push(index);
}
}
}
// Clean if needed.
for index in finished_ids {
self.tasks.remove(index);
warn!("Task {} has finished and is removed.", index);
}
if err_count > 0 {
ExecutionStatus::HadError(err_count)
} else {
ExecutionStatus::Success
}
}
/// Initialize all the tasks.
pub(crate) fn init(&mut self) {
debug!("Initializing {} task(s).", self.tasks.len());
for (_index, task) in self.tasks.iter_mut().enumerate() {
task.init(self.next_id);
self.next_id += 1;
}
}
/// Execute the `TaskGenerator` instance (if set).
///
/// This function will add the generated
fn run_task_gen(&mut self) {
match self.task_gen {
Some(ref mut tg) => {
// Execute only if it's time to execute it.
if tg.next_exec <= Utc::now().with_timezone(&self.timezone) {
match tg.run() {
Some(mut t) => {
t.init(self.next_id);
self.next_id += 1;
self.tasks.push(t);
}
None => { /* Do nothing */ }
}
}
}
None => { /* Do nothing */ }
}
}
/// Main execution loop.
pub fn run(&mut self) {
info!(
"Scheduler started. Total tasks currently in queue: {}",
self.tasks.len()
);
self.init();
loop {
self.run_task_gen();
match self.execute_tasks() {
ExecutionStatus::Success => { /* Do nothing */ }
ExecutionStatus::HadError(e) => {
error!("Execution round had {} errors.", e);
}
}
thread::sleep(Duration::from_millis(self.sleep as u64));
}
}
}
/// Module tests.
#[cfg(test)]
mod test {
use super::*;
use crate::TaskBuilder;
use chrono::Local;
use std::thread;
use std::time::Duration;
/// Test the normal functionality of a `TaskScheduler` instance.
#[test]
fn test_scheduler_normal_flow() {
// Create a new scheduler instance.
let mut scheduler = TaskScheduler::new(500, Local);
// Add a couple of tasks.
scheduler
.add_task(Task::new("* * * * * * *", None, Some(2), Local))
.add_task(Task::new("* * * * * * *", None, None, Local));
assert_eq!(scheduler.tasks.len(), 2);
// Initialize the tasks.
scheduler.init();
thread::sleep(Duration::from_millis(1000));
scheduler.execute_tasks();
assert_eq!(scheduler.tasks.len(), 2);
thread::sleep(Duration::from_millis(1000));
scheduler.execute_tasks();
assert_eq!(scheduler.tasks.len(), 1);
}
/// Test the normal functionality of a `TaskScheduler` instance,
/// in the case of task returning error status.
#[test]
fn test_scheduler_normal_flow_error_case() {
// Create a new scheduler instance.
let mut scheduler = TaskScheduler::new(500, Local);
// Create a task.
let mut task = Task::new("* * * * * * *", None, Some(1), Local);
task.add_step(None, || Ok(()));
// Return an error in the second step.
task.add_step(None, || Err(()));
// Add a task.
scheduler.add_task(task);
assert_eq!(scheduler.tasks.len(), 1);
// Initialize the task.
scheduler.init();
thread::sleep(Duration::from_millis(1000));
scheduler.execute_tasks();
// The task should be removed after it's execution circle.
assert_eq!(scheduler.tasks.len(), 0);
}
/// Test the normal functionality of a task generation function inside
/// a task scheduler.
#[test]
fn test_scheduler_with_generator() {
// Create a new scheduler instance.
let mut scheduler = TaskScheduler::new(500, Local);
// Add a task generator function that does now.
scheduler.set_task_gen(TaskGenerator::new("* * * * * * *", Local, || None));
// Should start with zero tasks.
assert_eq!(scheduler.tasks.len(), 0);
// Execute the task generator.
thread::sleep(Duration::from_millis(1000));
scheduler.run_task_gen();
// The number of tasks should be zero again.
assert_eq!(scheduler.tasks.len(), 0);
// Update the generator to actually create a new task.
scheduler.set_task_gen(TaskGenerator::new("* * * * * * *", Local, || {
// Run at second "1" of every minute.
// Create the task that will execute 2 total times.
// Return the task for the execution queue.
Some(
TaskBuilder::new(chrono::Local)
.every("* * * * * * *")
.build(),
)
}));
// Execute the task generator.
thread::sleep(Duration::from_millis(1000));
scheduler.run_task_gen();
// The number of tasks should be zero again.
assert_eq!(scheduler.tasks.len(), 1);
}
}